oop, figured it out
<script>
if( /Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent) ) {
Y.on('domready', function () {
var galleries = Y.Squarespace.GalleryManager.getGalleries();
for( i = 0; i<galleries.length; i++){
galleries[i].setAttrs({"autoplay":true})
}
});
}
</script>